1. Field of the Invention
The present invention relates to a printer for carrying a sheet of paper at least one side of which is printed and performing printing again on the sheet such as double-side printing for printing the other side of the printed side or multicolor printing for printing the printed side in ink of a different color.
2. Description of the Prior Art
Conventionally, double-side printing and multicolor printing by a printer having a single cylindrical print drum is widely performed. According to the double-side printing, a sheet of paper of which one side has been printed is set on a paper supply tray or the like and conveyed, and the other side is printed in the paper conveying process. According to the multicolor printing, a sheet of paper of which one side has been printed in ink of a certain color is set on a paper supply tray or the like and conveyed, and the printed side is printed in ink of another color during the paper conveying process.
In the case of performing the double-side printing or the multicolor printing, what is called a re-transferred smudge (roller track smudge) occurs on the printed sheet as follows. When a rotating member (such as pick-up roller, separation roller, resist roller, or press roller) for conveying the printed sheet comes into contact with undried ink on the printed side of the printed sheet, the undried ink is transferred to the periphery of the rotating member and the undried ink transferred to the rotating member is transferred again to the printed side of the printed sheet.
In order to prevent the occurrence of the retransfer smudge, the double-side printing or multicolor printing is performed after sufficiently drying the ink on the printed side of the printed sheet.
When the double-side printing or multicolor printing is performed after the ink on the printed side of the printed sheet is sufficiently dried, the waiting time is long and it causes a problem such that the efficiency of the double-side printing and the multicolor printing deteriorates.
It is an object of the present invention to prevent a smudge occurring when a printed sheet of paper at least whose one side has been printed is conveyed and printed again for double-side printing or multicolor printing.
Another object of the present invention is to improve work efficiency of a case where a printed sheet of paper at least whose one side has been printed is conveyed and printed again for double-side printing or multicolor printing.
According to a printer of the present invention, each of rotating members for feeding a sheet of paper which are disposed along a guide path including a printing unit with a removing member which rotates while being in contact with the periphery of the rotating member so as to spread ink passed on the rotating member, so that the removing member removes a part of the ink from the rotating member.
According to another aspect of the present invention, the periphery of one of the rotating members is made of a material to which ink is not easily adhered. The rotating members are disposed via a guide path and rotate, so that the rotating members contribute to convey a sheet of paper. The guide path includes a printing unit.
According to another aspect of the present invention, a pair of first and second resist rollers disposed upstream of the printing unit via a guide path are provided. The periphery of the first resist roller is made of a material to which ink is not easily adhered and the periphery of the second resist roller is made of a material having elasticity to assure a paper conveying force. Another pair of first and second resist rollers disposed upstream of the printing unit via the guide path are also provided. The periphery of the first resist roller is made of a material to which ink is not easily adhered and the periphery of the second resist roller is made of a material having elasticity to assure a paper conveying force. The disposing positions of the first and second resist rollers with respect to the guide path as a center are opposite to those of the foregoing pair of resist rollers. The first and second resist rollers in either one of the pairs of resist rollers are allowed to be in contact with each other. The first and second resist rollers in the other pair of resist rollers are allowed to be apart from each other.
According to further aspect of the present invention, a pair of first and second resist rollers disposed upstream of the printing unit in the guide path of a sheet of paper are provided via the guide path. The periphery of the first resist roller is made of a material to which ink is not easily adhered and the periphery of the second resist roller is made of a material having elasticity to assure a paper conveying force. The positions of the first and second resist rollers with respect to the guide path as a center are reversed as appropriate.